The urinary bladder develops from
the urogenital sinus. This sinus is
connected to the umbilicus via the urachus. As
the development of the sinus continues, the urinary bladder is formed
anteriorly and the urogenital sinus is
left posteriorly. Initially the urogenital
sinus and the hindgut are derived from a common sac known as the
cloaca.

The
urogenital sinus continues its development and assists in the
formation of the reproductive tract. The urinary bladder becomes separated
from the urogenital sinus. The
cloaca is an endodermal structure hence the
bladder is also endodermal being derived from it. The bladder is connected
to the umbilicus via the urachus, the median
umbilical ligament. The urachus is patent, 1/3rd
of its length from the bladder. It may finally develop into cysts, sinus
or fistula if it does not completely disappear which may then connect the
umbilicus with the urinary bladder.

The ureters are connected to the
bladder at the lateral angles of the trigone while the
Wolffian duct become connected to or
maintain their connection to the urogenital
sinus at its junction with the urinary bladder. The bladder mucosa may
sometimes be found in the inferior umbilical abdominal wall where it is
called ectopia vesicae.